From Science & Research
From Science & Research Compostable polymers are increasingly found in applications such as packaging, disposable nonwovens and hygiene products, consumer goods and agricultural products. A wide variety of compostable polymers have been developed, derived both from petrochemical and renewable sources. But, what do we know about how these materials behave in other environments or conditions outside of industrial composting facilities? In 2018, the European Parliament introduced the new ‘European Strategy for Plastics in a Circular Economy’, in which the opportunities and risks associated with the growing use of plastics with biodegradable properties, have also been acknowledged. In the absence of clear labelling or marking for consumers and without suitable waste collection and treatment options, these plastics could aggravate the leakage of plastics into the environment and cause mechanical recycling problems. On the other hand, the European Strategy states that biodegradable plastics can certainly have a role in some applications, and that innovation efforts in this field are welcome but that the behaviour and consequences of their biodegradability must be demonstrated. This article will present the main findings of a study on the degree of disintegration of a compostable polymer and a visual analysis of the material degradation in different environmental conditions. It will present different tests carried out under industrial composting conditions, home compost conditions, composting conditions in a lab-scale test (aggressive synthetic solid) and in soil (natural environment) at two different temperatures. Furthermore, the ecotoxicological effects of the environment after the disintegration process was evaluated to obtain a full understanding of the behaviour of these polymers. The present study revealed that two main aspects determine the degree of disintegration of a compostable biopolymer (PLA and PBTA blend): on the one hand, the aggressiveness of the medium (microbial activity) and on the other hand, the temperature. The most aggressive medium, an enriched synthetic solid, gave rise to average disintegration degrees of 96.09 %, followed by natural compost of vegetable origin and a normalized soil, thus reaching disintegration degrees of 87.76 % and 72.05 % respectively at thermophilic temperature (58 ºC). By: Elena Domínguez Researcher, Sustainability and Industrial Recovery department AIMPLAS Paterna, Valencia, Spain Compostable plastics’ behaviour in different environmental conditions Figure 1. Degree of disintegration of the material tested in different environments and thermophilic conditions (58 ºC) Figure 2. Degree of disintegration of the material tested in different environments and mesophilic conditions (25 ºC) 58ºC day 7 day 37 day 69 day 90 25ºC day 7 day 90 Synthetic Solid Synthetic Solid Normalized Soil Normalized Soil Compost Compost 30 bioplastics MAGAZINE [06/18] Vol. 13
From Science & Research At a mesophilic temperature of 25 ºC , the materials did not achieve degradation in any of the environments studied. In this study, the ecotoxicological effects were evaluated in a fast-growing plant species (Ray Grass) from the media where disintegration had occurred. None of the media in which the polymeric material had disintegrated produced a toxic effect on the species in question and the vegetal biomass reached a germination and growth rate of over 90 % with respect to the reference substrate. A limitation in the use of bioplastics is the existing confusion about the behaviour of materials in different conditions. An industrially compostable material is not necessarily able to biodegrade under other temperature conditions or in other environmental conditions. Currently, there are international schemes for the certification of biodegradable materials in different environments that may cause confusion in this sector. These schemes guarantee to customers the biodegradability of a material in certain conditions according to international standards. In order to enable the correct communication of biodegradable polymers through product ecolabelling, there are different standards of biodegradation determination in different environments (compost, soil, etc.), which have been used to create certification schemes that specify the requirements to be met in order to attain the corresponding certificate and product labelling. Manufacturers and suppliers in Europe have relied on the neutral and independent certifications by DIN CERTCO and TÜV Austria for many years. Certifications from these agencies send a message to consumers about the quality of the products and can serve as guidance when making purchasing decisions. These independent bodies are able to specify the correct biodegradation environment for final products thanks to verification marks. The most common ecolabel assigned is that of compostability in industrial facilities (at a temperature of approximately 60 ºC). The aforementioned bodies grant their own compostability ecolabels together with European Bioplastics association’s Seedling compostability mark. Both marks, can be used individually, alternatively or simultaneously, and document the biodegradability, among other aspects, of a final product or material in industrial composting facilities. A material that is compostable in industrial composting facilities will not necessarily compost in home composting conditions, where, among other things, the temperature is considerably lower (approximately 25 ºC). Different certificates are obtainable for different conditions and environments: biodegradable materials and products can be certified as degradable in soil, saltwater or fresh water. Any supplier who invests in adding this functionality to their product or packaging should have the opportunity to have this information verified according to international standards, obviously without encouraging consumers to litter. Biodegradability in the soil offers huge benefits for agricultural and horticultural products, as they can be left to break down in situ after being used. In 2018, standard EN 17033 [1] was developed, which outlines the requirements to be met by agricultural mulch films, an application in which biodegradability in soil entails the end of life of materials, thus reducing soil contamination due to mismanagement on the part of humans. AIMPLAS, the Plastics Technology Centre, based in Spain, is now in the process of becoming a laboratory recognized by TÜV Austria, after which it will support the manufacturers in the verification process required for the different ecolabels, evaluating the requirements necessary to fulfil each point of the certification schemes according to international regulations. Furthermore, as a quality aspect, Aimplas has a testing laboratory accredited by ENAC with accreditation no 56/LE156 in conformity with the EN ISO/IEC 17025 standard. Moreover, Aimplas has the highest number of ENAC accreditations for plastics according to the ISO 17025 standard at national level. ENAC accreditations are recognized in over 50 countries, since it is a signatory of the Mutual Recognition Agreements arranged at an international level among accreditation bodies all over the world. These agreements include practically the whole of the EU, USA, Canada, Japan, China and Australia, among others. [1] EN 17033: 2018. Plastics - Biodegradable mulch films for use in agriculture and horticulture - Requirements and test methods. www.aimplas.es Figure 4. AIMPLAS’ equipment for simulation of conditions of biodegradation or disintegration tests. bioplastics MAGAZINE [06/18] Vol. 13 31
